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September 10, 2025Open Access

Long-Term Snow Cover Change in the Qilian Mountains (1986–2024): A High-Resolution Landsat-Based Analysis

EHEnwei HuangNorthwest Normal University GZGuofeng ZhuInstitute of Environment and Sustainable Development in Agriculture YWYuhao WangChinese Academy of Sciences

Key Points

The mean annual snow cover extent in the Qilian Mountains showed a slight declining trend over the years.
Significant upward migration of the snowline was observed, with important elevation-dependent changes in snow cover.
Observations revealed good correlation between Landsat and MODIS data, indicating systematic differences in mountainous regions.
The findings underscore the complex response of snow systems in the Qilian Mountains to global warming and its implications.

Abstract

Snow cover, as a critical component of the cryosphere, serves as a vital water resource for arid regions in Northwest China. The Qilian Mountains (QLM), situated on the northeastern margin of the Tibetan Plateau, function as an important ecological barrier and water conservation area in western China. This study presents the first high-resolution historical snow cover product developed specifically for the QLM, utilizing a multi-level snow classification algorithm tailored to the complex topography of the region. By employing Landsat satellite data from 1986–2024, we constructed a comprehensive 39-year snow cover dataset at a resolution of 30 m. A dual adaptive cloud masking strategy and spatial interpolation techniques were employed to effectively address cloud contamination and data gaps prevalent in mountainous regions. The spatiotemporal characteristics and driving mechanisms of snow cover changes in the QLM were systematically analyzed using Sen–Theil trend analysis and Mann–Kendall tests. The results reveal the following: (1) The mean annual snow cover extent in the QLM was 15.73% during 1986–2024, exhibiting a slight declining trend (−0.046% yr−1), though statistically insignificant (p = 0.215); (2) The snowline showed significant upward migration, with mean elevation and minimum elevation rising at rates of 3.98 m yr−1 and 2.81 m yr−1, respectively; (3) Elevation-dependent variations were observed, with significant snow cover decline in high-altitude (>5000 m) and low-altitude (2000–3500 m) regions, while mid-altitude areas remained relatively stable; (4) Comparison with MODIS data demonstrated good correlation (r = 0.828) but revealed systematic differences (RMSE = 12.88%), with MODIS showing underestimation in mountainous environments (Bias: −8.06%). This study elucidates the complex response mechanisms of the QLM snow system under global warming, providing scientific evidence for regional water resource management and climate change adaptation strategies.

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